And not into nature only; but he plunged also into human personality, and became above all a painter of portraits; faces of a modelling more skilful than has been seen before or since, embodied with a reality which almost amounts to illusion, on the dark air. To take a character as it was, and delicately sound its stops, suited one so curious in observation, curious in invention. He painted thus the portraits of Ludovico's [112] mistresses, Lucretia Crivelli and Cecilia Galerani the poetess, of Ludovico himself, and the Duchess Beatrice. The portrait of Cecilia Galerani is lost, but that of Lucretia Crivelli has been identified with La Belle Feronière of the Louvre, and Ludovico's pale, anxious face still remains in the Ambrosian library. Opposite is the portrait of Beatrice d'Este, in whom Leonardo seems to have caught some presentiment of early death, painting her precise and grave, full of the refinement of the dead, in sad earth-coloured raiment, set with pale stones. Sometimes this curiosity came in conflict with the desire of beauty; it tended to make him go too far below that outside of things in which art really begins and ends. This struggle between the reason and its ideas, and the senses, the desire of beauty, is the key to Leonardo's life at Milan--his restlessness, his endless re-touchings, his odd experiments with colour. How much must he leave unfinished, how much recommence! His problem was the transmutation of ideas into images. What he had attained so far had been the mastery of that earlier Florentine style, with its naïve and limited sensuousness. Now he was to entertain in this narrow medium those divinations of a humanity too wide for it, that larger vision of the opening world, which is only not too much for the great, irregular art of Shakespeare; and everywhere the effort is visible in the work of his hands. This agitation, this [113] perpetual delay, give him an air of weariness and ennui. To others he seems to be aiming at an impossible effect, to do something that art, that painting, can never do. Often the expression of physical beauty at this or that point seems strained and marred in the effort, as in those heavy German foreheads-- too heavy and German for perfect beauty.